Cooperative video game in the context of "Non-player character"

A multiplayer video game is a video game in which more than one person can play in the same game environment at the same time, either locally on the same computing system (couch co-op), on different computing systems via a local area network, or via a wide area network, most commonly the Internet (e.g. World of Warcraft, Call of Duty, DayZ). Multiplayer games usually require players to share a single game system or use networking technology to play together over a greater distance; players may compete against one or more human contestants, work cooperatively with a human partner to achieve a common goal, or supervise other players' activity. Due to multiplayer games allowing players to interact with other individuals, they provide an element of social communication absent from single-player games.

The history of multiplayer video games extends over several decades, tracing back to the emergence of electronic gaming in the mid-20th century. One of the earliest instances of multiplayer interaction was witnessed with the development of Spacewar! in 1962 for the DEC PDP-1 computer by Steve Russell and colleagues at the MIT. During the late 1970s and early 1980s, multiplayer gaming gained momentum within the arcade scene with classics like Pong and Tank. The transition to home gaming consoles in the 1980s further popularized multiplayer gaming. Titles like Super Mario Bros. for the NES and Golden Axe for the Sega Genesis introduced cooperative and competitive gameplay. Additionally, LAN gaming emerged in the late 1980s, enabling players to connect multiple computers for multiplayer gameplay, popularized by titles like Doom and Warcraft: Orcs & Humans. Players can also play together in the same room using splitscreen.

Ikaruga (Japanese: 斑鳩; lit. 'Japanese grosbeak') is a bullet hell shoot 'em up developed by Treasure. It is the spiritual sequel to Radiant Silvergun (1998) and was originally released in Japanese arcades in December 2001. The story follows a rebel pilot named Shinra as he battles an enemy nation using a specially designed fighter called the Ikaruga which can flip between two polarities, black and white. This polarity mechanism is the game's key feature and the foundation for its stage and enemy design. All enemies and bullets in the game are either black or white. Bullets which are the same color as the player are absorbed while the others will kill the player. The game features both single-player and cooperative modes.

Development on Ikaruga began during director Hiroshi Iuchi's off-hours while Treasure was busy developing Sin and Punishment (2000). Titled "Project RS2", the game began as a sequel to Radiant Silvergun, and borrows many elements from it as well as the polarity mechanism from Treasure's Silhouette Mirage (1997). During the game's prototype stages, the player's ammo was limited. The bullet absorption mechanism was used as a means to refill ammo. However, this was found to be weak as it created too many breaks in the action so it was later added as an additional mode in home ports. In tradition with Treasure's game design philosophy, Ikaruga was intentionally crafted to challenge the conventions of standard game design and develop a new type of shooting game. All together, five Treasure staff worked on Ikaruga, as well as three support staff from G.rev.